If you hear Dio's "Wryyyyyy", it was successful. Proceed to "Save and Exit", and the new playable characters will be available on the opposite sides of the character selection screen. They include Shadow Dio, Kan, New Kakyoin, Hol Horse with Voing, Robber Soul, and JoJo.

Hints

Achievements
Complete each achievement to get the allotted gamerscore:

Crash and Burn (20) - Down an opponent while they are Stand Crashed.
Mad with Power (20) - Down an opponent with a Super Combo.
Never Saw it Coming (40) - K.O. N'Dool via Perfect in bonus stage.
Out of the Cage (20) - Win one Ranked Match over Xbox LIVE.
Patty Cake, Patty Cake (40) - Activate a Blazing Fists match.
Show and Tell (20) - Upload replay data.
Standing the Test of Time (100) - Complete Story Mode or Challenge Mode for any character on any difficulty without using continues.
Stardust Crusaders (40) - Win a fight with 22 different characters.
Strong and Attractive (20) - Raise Mahrahia's magnetic power to maximum level.
The Kid Gloves are Off (20) - Down an opponent while in child form.
The World is Your Oyster (40) - Counter a time-freeze.
This is Where You Fall Down (20) - Down an opponent without using a Super Combo or Tandem Attack.

Fight Death 13
You can't lose any matches, and you must use of of the main six characters (Jotaro, Joseph, Avdol, Iggy, Polnareff and Kakyoin). Starting from the first fight, ending with the fifth. The game will say "here comes a new challenger" and then death 13's name will appear.